<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<script type="text/javascript">

	window.onload = function(){

		var oPop = document.getElementById('pop');
		var oShut = document.getElementById('shutoff');




		/*

		setTimeout(showpop,4000);


		function showpop(){

			oPop.style.display = 'block';

		}


		*/

		 setTimeout(function(){
		 	oPop.style.display = 'block';

		 },3000);


		

		oShut.onclick = function(){
			oPop.style.display = 'none';
		}



	}





	</script>
	<style type="text/css">

		.pop_con{
			display:none;
		}
		
		.pop{
			width:400px;
			height:300px;
			background-color:#fff;
			border:1px solid #000;
			position:fixed;
			left:50%;
			top:50%;
			margin-left:-200px;
			margin-top:-150px;
			z-index:9999;
		}

		.mask{
			position:fixed;
			width:100%;
			height:100%;
			background-color:#000;
			left:0;
			top:0;
			opacity:0.3;
			filter:alpha(opacity=30);
			z-index:9990;		
		}


	</style>
</head>
<body>
	<h1>首页标题</h1>
	<p>页面内容</p>



	<div class="pop_con" id="pop">
		<div class="pop">
			<h3>提示信息！</h3>
			<a href="#" id="shutoff">关闭</a>
		</div>
		
		<div class="mask"></div>
	</div>
	
</body>
</html>